feat(backend): add handler to detect disonnecction

Author: JavierRibaldelRio

backend/cmd/config.toml

@@ -20,6 +20,7 @@ validate = true # Execute ADJ validator before starting backend
 # Transport Configuration
 [transport]
 propagate_fault = true
+max_packet_interval_us = 100000 # Max interval (us) between two UDP packets of the same id before propagating a fault (0 disables the check)
 
 # TCP Configuration
 # These settings control how the backend reconnects to boards when connections are lost

backend/cmd/dev-config.toml

@@ -22,6 +22,7 @@ validate = true # Execute ADJ validator before starting backend
 # Transport Configuration
 [transport]
 propagate_fault = false
+max_packet_interval_us = 100 # Max interval (us) between two UDP packets of the same id before propagating a fault (0 disables the check)
 
 # TCP Configuration
 # These settings control how the backend reconnects to boards when connections are lost

backend/cmd/main.go

@@ -4,6 +4,7 @@ import (
 	_ "net/http/pprof"
 	"os"
 	"os/signal"
+	"time"
 
 	"github.com/HyperloopUPV-H8/h9-backend/internal/config"
 	"github.com/HyperloopUPV-H8/h9-backend/internal/flags"
@@ -97,6 +98,7 @@ func main() {
 	// <--- transport --->
 	transp := transport.NewTransport(trace.Logger)
 	transp.SetpropagateFault(config.Transport.PropagateFault)
+	transp.SetMaxPacketInterval(time.Duration(config.Transport.MaxPacketIntervalUs) * time.Microsecond)
 
 	// <--- vehicle --->
 	err = configureVehicle(

backend/internal/config/config_types.go

@@ -12,7 +12,8 @@ type Adj struct {
 }
 
 type Transport struct {
-	PropagateFault bool `toml:"propagate_fault"`
+	PropagateFault      bool  `toml:"propagate_fault"`
+	MaxPacketIntervalUs int64 `toml:"max_packet_interval_us"`
 }
 
 type TCP struct {

backend/pkg/transport/constructor.go

@@ -3,6 +3,7 @@ package transport
 import (
 	"net"
 	"sync"
+	"time"
 
 	"github.com/HyperloopUPV-H8/h9-backend/pkg/abstraction"
 	"github.com/HyperloopUPV-H8/h9-backend/pkg/transport/presentation"
@@ -16,6 +17,8 @@ func NewTransport(baseLogger zerolog.Logger) *Transport {
 		idToTarget:    make(map[abstraction.PacketId]abstraction.TransportTarget),
 		ipToTarget:    make(map[string]abstraction.TransportTarget),
 
+		lastPacketTime: make(map[abstraction.PacketId]time.Time),
+
 		logger:  baseLogger,
 		errChan: make(chan error, 100),
 	}

backend/pkg/transport/transport.go

@@ -34,7 +34,9 @@ type Transport struct {
 	ipToTarget map[string]abstraction.TransportTarget
 	idToTarget map[abstraction.PacketId]abstraction.TransportTarget
 
-	propagateFault bool
+	propagateFault    bool
+	maxPacketInterval time.Duration
+	lastPacketTime    map[abstraction.PacketId]time.Time
 
 	api abstraction.TransportAPI
 
@@ -413,6 +415,8 @@ func (transport *Transport) handleUDPPacket(udpPacket udp.Packet) {
 		transport.replicateFault(packet, transport.logger)
 	}
 
+	transport.checkPacketInterval(packet.Id(), udpPacket.Timestamp)
+
 	// Send notification
 	transport.api.Notification(NewPacketNotification(packet, srcAddr, dstAddr, udpPacket.Timestamp))
 
@@ -421,6 +425,34 @@ func (transport *Transport) handleUDPPacket(udpPacket udp.Packet) {
 	}
 }
 
+// checkPacketInterval propagates a fault when the time between two consecutive
+// UDP packets with the same id exceeds maxPacketInterval. Fault packets (id 0)
+// are excluded. lastPacketTime needs no locking because this is only called
+// from the HandleUDPServer goroutine.
+func (transport *Transport) checkPacketInterval(id abstraction.PacketId, timestamp time.Time) {
+	if !transport.propagateFault || transport.maxPacketInterval <= 0 || id == 0 {
+		return
+	}
+
+	last, seen := transport.lastPacketTime[id]
+	transport.lastPacketTime[id] = timestamp
+	if !seen {
+		return
+	}
+
+	interval := timestamp.Sub(last)
+	if interval <= transport.maxPacketInterval {
+		return
+	}
+
+	transport.logger.Warn().
+		Uint16("id", uint16(id)).
+		Dur("interval", interval).
+		Dur("threshold", transport.maxPacketInterval).
+		Msg("packet interval exceeded, propagating fault")
+	transport.SendFault()
+}
+
 // handleConversation is called when the sniffer detects a new conversation and handles its specific packets
 func (transport *Transport) handleConversation(socket network.Socket, reader io.Reader) {
 	srcAddr := fmt.Sprintf("%s:%d", socket.SrcIP, socket.SrcPort)
@@ -473,3 +505,10 @@ func (transport *Transport) SendFault() {
 func (transport *Transport) SetpropagateFault(enabled bool) {
 	transport.propagateFault = enabled
 }
+
+// SetMaxPacketInterval sets the maximum allowed interval between two
+// consecutive UDP packets of the same id before a fault is propagated.
+// A non-positive interval disables the check.
+func (transport *Transport) SetMaxPacketInterval(interval time.Duration) {
+	transport.maxPacketInterval = interval
+}